Taking the term in its widest sense matter signifies that out of which anything is made or composed. Thus the original meaning of ule. (Homer) is "wood", in the sense of "grove" or "forest"; and hence, derivatively, "wood cut down" or timber. The Latin materia, as opposed to lignum (wood used for fuel), has also the meaning of timber for building purposes. In modern languages this word (as signifying raw material) is used in a similar way. Matter is thus one of the elements of the becoming and continued being of an artificial product. The architect employs timber in the building of his house; the shoemaker fashions his shoes from leather. It will be observed that, as an intrinsic element, matter connotes composition, and is most easily studied in a consideration of the nature of change. This is treated ex professo in the article on Cause (q.v.). It will, however, be necessary to touch upon it briefly again here, since matter can only be rationally treated in so far as it is a correlate. The present article will therefore be divided into paragraphs giving the scholastic doctrine under the following heads—(1) Secondary Matter (in accidental change); (2) Primordial Matter (in substantial change); (3) The Nature of Primordial Matter; (4) Privation; (5) Permanent Matter; (6) The Unity of Matter; (7) Matter as the Principle of Individuation; (8) The Causality of Matter; (9) Variant Theories.

(1) Secondary Matter

—Accepting matter in the original sense given above, Aristotle defines the "material cause" oion o chalkos tou andriantos kai o arguros tes phiales.. That the form of the statue is realized in the bronze, that the bronze is the subject of the form, is sensibly evident. These two elements of the statue or bowl are the intrinsic "causes" of its being what it is. With the addition of the efficient and final cause (and of privation) they constitute the whole doctrine of its aetiology, and are invoked as a sufficient explanation of "accidental" change. There is no difficulty in understanding such a doctrine. The determinable "matter" (here, in scholastic terminology, more properly substance) is the concrete reality—brass or white metal—susceptible of determination to a particular mode of being. The determinant is the artificial shape or form actually visible. The "matter" remains substantially the same before, throughout, and after its fashioning.

(2) Primordial Matter

—The explanation is not so obvious when it is extended to cover substantial change. It is indeed true that already, in speaking of the "matter" of accidental change (substance), we go beyond the experience given in sense perception. But, when we attempt to deal with the elements of corporeal substance, we proceed still farther in the process of abstraction. It is impossible to represent to ourselves either primordial matter or substantial form. Any attempt to do so inevitably results in a play of imagination that tends to falsify their nature, for they are not imaginable. The proper objects of our understanding are the essences of those bodies with which we are surrounded (cf. S. Thomas, "De Principio Individuationis"). We have, however, no intuitive knowledge of these, nor of their principles. We may reason about them, indeed, and must so reason if we wish to explain the possibility of change; but to imagine is to court the danger of arriving at entirely false conclusions. Hence whatever may be asserted with regard to primordial matter must necessarily be the result of pure and abstract reasoning upon the concrete data furnished by sense. It is an inexisting principle invoked to account for substantial alteration. But, as St. Thomas Aquinas remarks, whatever knowledge of it we may acquire is reached only by its analogy to "form" (ibid.). The two are the inseparable constituents of corporeal beings. The teaching of Aquinas may be briefly set out here as embodying that also of Aristotle, with which it is in the main identical. It is the teaching commonly received in the School; though various other opinions, to which allusion will be made later, are to be found advanced both before and after its formulation by Aquinas.

(3) The Nature of Primordial Matter

—For St. Thomas primordial matter is the common ground of substantial change, the element of indetermination in corporeal beings. It is a pure potentiality, or determinability, void of substantiality, of quality, of quantity, and of all the other accidents that determine sensible being. It is not created, neither is it creatable, but rather concreatable and concreated with Form, (q.v.), to which it is opposed as a correlate, as one of the essential "intrinsic constituents" (De Principiis Naturae) of those corporeal beings in whose existence the act of creation terminates. Similarly it is not generated, neither does it corrupt in substantial change, since all generation and corruption is a transition in which one substance becomes another, and consequently can only take place in changes of composite subjects. It is produced out of nothing and can only cease to be by falling back into nothingness (De Natures Materiae, i). Its potentiality is not a property superadded to its essence, for it is a potentiality towards substantial being (In I Phys., Lect. 14). A stronger statement is to be found in "QQ. Disp.", III, Q. iv., a. 2 ad 4: "The relation of primordial matter ... to passive potentiality is as that of God... to active (potentiam activam). Therefore matter is its passivity as God is His activity". It is clear throughout that St. Thomas has here in view primordial matter in the uttermost degree of abstraction. Indeed, he is explicit upon the point. "That is commonly called primordial matter which is in the category of substance as a potentiality cognized apart from all species and form, and even from privation; yet susceptive of forms and privations" (De spiritual. creat., Q. i, a. 1).

If we were "obliged to define its essence, it would have for specific difference its relation to form, and for genus its substantiality" (Quod., IX, a. 6. 3). And again: "It has its being by reason of that which comes to it, since in itself it has incomplete, or rather no being at all" (De Princip. Naturae). Such information is mainly negative in character, and the phrases employed by St. Thomas show that there is a certain difficulty in expressing exactly the nature of the principle under consideration. This difficulty evidently arises from the imagination, and with imagination the philosophy of matter has nothing to do. We must begin with the real, the concrete being. To explain this, and the changes it is capable of undergoing, we must infer the coexistence of matter and form determinable and determinant. We may then strip matter, by abstraction, of this or that determination; we may consider it apart from all its determinations. But once attempt to consider it apart from that analogy by which alone we can know it, once strip it mentally of its determinability by form, and nothing—absolute nothing—remains. For matter is neither realizable nor thinkable without its correlative. The proper object of intelligence, and likewise the subject of being, is Ens, Verum. Hence St. Thomas teaches further that primordial matter is "a substantial reality" (i.e., a reality reductively belonging to the category of substance), "potential towards all forms, and, under the action of a fit and proportioned efficient cause, determinable to any species of corporeal substance" (In VII Met., sect. 2); and, again: "It is never stripped of form and privation; now it is under one form now under another. Of itself it can never exist" (De Princip. Natur.). What has been said may appear to deny to matter the reality that is predicated of it. This is not the case. As the determinable element in corporeal substance it must have a reality that is not that of the determining form. The mind by abstraction may consider it as potential to any form, but can never overstep the limit of its potentiality as inexistent (cf. Aristotle's tienuparchontos (Phys., iii, 194b, 16) and realized in bodies without finding itself contemplating absolute nothingness. Of itself matter can never exist, and consequently of itself it can never be thought.

(4) Privation

—The use of the term "privation" by Aquinas brings us to an exceedingly interesting consideration. While primordial matter, as "understood" without any form or privation, is an indifferent potentiality towards information by any corporeal form, the same matter, considered as realized by a given form, and actually existing, does not connote this indefinite capacity of information. There is, in fact, a certain rhythmic evolution of forms observable in nature. By electrolysis only oxygen and hydrogen can be obtained from water; from oxygen and hydrogen in definite proportions only water is generated. This fact St. Thomas expresses in the physical terms of his time: "If any particular matter, e.g. fire or air, were despoiled of its form, it is manifest that the potentiality towards other educible forms remaining in it would not be so ample, as is the case in regard to matter (considered) universally" (De Nat. Mat., v). The consideration gives us the signification of "privation", as used in the theory of substantial change. Matter is "deprived" of the form or forms towards which alone it is potential when actually existing in some one or other state of determination. Hence the distinction that is found in the Opuscule "De Principiis Naturae".

(5) Permanent Matter

—"Matter that does not connote a privation is permanent, whereas that which does is transient". The connotation of a privation limits primordial matter to that which is realized by a form disposing it towards realization by certain other definite forms. "Privation" is the absence of those forms. Permanent matter is matter considered in the highest degree of abstraction, and connoting thereby no more than its correlation to form in general.

(6) The Unity of Matter

—Further, this (permanent) matter is said to be one; not however, in the sense of a numerical unity. Every corporeal being is held to result from the union of matter and form. There are in consequence as many distinct individual realized portions of matter as there are distinct bodies (atoms, for example) in the universe. Nevertheless, when the severally determining principles and privations are abstracted from, when matter is cognized in its greatest abstraction, it is cognized as possessing a logical unity. It is understood without any of those dispositions that make it differ numerically with the multiplication of bodies (De Principiis Naturae).

(7) Matter as the Principle of Individuation

—More important is the doctrine that grounds in matter the numerical distinction of specifically identical corporeal beings. In the general doctrine of St. Thomas, the individual—"this thing" (hoc aliquid)—is a primordial substance, individualized by the fact that it is what it is ("Substantia individuatur per seipsam": Summa, Pars I, Q. xxix, a. 1). It is intrinsically complete, capable of subsisting in itself as the subject of accidents in the ontological order, and of predicates in the logical. It is undivided in itself, distinct from all other, incommunicable (cf. De Principio Individuationis). These characteristic notes are realized in the case of two substances that differ by essence. Thus, for St. Thomas, no two Angels (q.v.) are specifically identical (Summa, Pars I, Q. 1, a. 4). More than this, even a corporeal form, however material and low in the hierarchy of forms, would not be other than unique in its species, if it could exist (or be thought), apart from its relation to matter (cf. De Spiritual. Creaturis, Q. i, a. 8). Whiteness, if it could subsist without any subject, would be unique. If a plurality of such accidental forms could subsist they also would differ specifically—as whiteness, redness, etc. But this distinction evidently does not obtain in the case of a number of individuals belonging to one species. They are essentially identical. How is it, then, that they can constitute a plurality? The answer given by St. Thomas to this question is his doctrine of the Principle of Individuation. Whereas the plurality of simple substances, or "forms", is due to a real difference of their essences (as a triangle differs from a circle), the plurality of identical essences, or "forms", supposes an intrinsic principle of individuation for each (as two triangles realized in two pieces of wood). Thus, simple substances differ by reason of their nature, formally; while composite ones differ by reason of an inherent principle, materially. They are multiplied within a given species by reason of matter.

At this point a peculiarly delicate question arises. The abstract essence of man connotes matter. If, then, primordial matter be the principle of individuation, it would seem that the abstract essence is already individualized. Wherein would lie the admitted difference between the species and the individual? On the other hand, if that be not the case, it would appear equally evident that, in adding to the individual a principle not contained in the abstract essence, it would no longer be an object of classification in the species. It would not be merely the concrete realization of the essence, but something more. In either case the doctrine would seem to be incompatible with modern Realism. St. Thomas avoids the difficulty by teaching that matter is the principle of individuation, but only as correlated to quantity. The expressions that he uses are "materia signata", "materia subjectadimensioni" (In Boeth. de Trin., Q. iv, a. 2), "materia sub certis dimensionibus" (De Nat. Mat., iii). This needs some explanation. Quantity, as such, is an accident; and it is evident that no accident can account for the individuality of its own subject. But quantity results in corporeal substance by reason of matter. Primordial matter, then, considered as such, has a relation to quantity consequent upon its necessary relation to form (De Nat. Mat., iv). When actuated by form it has dimensions—the "inseparable concomitants that determine it in time and place" (De Princip. Individ.). The abstract essence, then, embracing matter as it does form, will connote an aptitude or potentiality towards a quantitative determination, necessarily resultant in each concrete subject realized.

Here, as formerly, the fact must not be lost sight of that the reasoning begins with the concrete bodies actually existing in nature. It is by an abstraction that we consider matter without the actual quantity that it always exhibits when realized in corporeal substance. Peter, as a matter of fact, differs from Paul, yet they are specifically identical as rational animals. Peter is "this" man, and Paul is "that", but "this" and "that", because "here" and "there". "Form is not individuated in that it is received in matter, but only in that it is received in this or that distinct matter, and determined to here and now" (In Boeth. de Trin. Q. iv, a. 1). It is evident that "here" and "now" are the immediate and inseparable signs for us of the individual. They indicate "hoec taro et ossa". And they are only possible by reason of (informed) matter, the ground of divisibility and location in space. Still, it must be noted that "materia signata quantitate" is not to be understood as primordial matter having an aptitude towards fixed and invariable dimensions. The determined dimensions that are found in the existing subject are to be attributed, St. Thomas teaches, to matter as "individuated by indeterminate dimensions preunderstood in it" ("In Boeth. de Trin.", Q. iv, a. 2; "De Nat. Mat.", vii). This remark explains how an individual (as Peter) can vary in dimension without varying in identity; and at the same time gives the reply of Aquinas to the difficulty raised above. Primordial matter, as connoted in the essence, has an aptitude towards indeterminate dimensions. These dimensions when realized are the ground of the determined dimensions (ibid.) that make the individual hic et nunc an object of sense-perception (De Nat. Materiae, iii).

(8) The Causality of Matter

—Since Primordial Matter is numbered among the causes of corporeal being, the nature of its causality remains to be considered. (See Cause.) All scholastics admit its concurrence with form, as an intrinsic cause; but they are not unanimous as to the precise part it plays. For Suarez it is unitive; for John of St. Thomas receptive. The Conimbricences place its causality in both notes. It would, perhaps, seem more consonant with the doctrine of St. Thomas to adopt Cardinal Mercier's opinion that the causality of matter is first receptive and second unitive; provided always that its essential potentiality be never lost sight of.

(9) Variant Theories of Matter

—The teaching of Aquinas has been given as substantially identical with that of Aristotle. The main point of divergence lies in the opinion of Aristotle that the world—and consequently matter—is eternal. St. Thomas, in accepting the doctrine of Creation, denies the eternity of primordial matter. It is interesting to note how this doctrine of matter, as the potential, or determinable, element in change, unites and corrects the views of Heraclitus, Parmenides, and Plato. The perpetual flux of the first is found in the continual transformations that take place in material nature. The changeless "one" of the second is recognized in the abstract essences eternally identical with themselves. And the world of "ideas" of Plato is assigned its place as a world of intellectual abstractions practiced upon the bodies that fall under the observation of the senses. The universal is immanent in the individual and multiplied by reason of its matter. In the system of Plato, matter (me on, apeiron: the "formless and invisible") is also the condition under which being becomes the object of the senses. It gives to being all its imperfections. It is by a mixture of being and nothingness, rather than by the realization of a potentiality, that sensible things exist. While for Aristotle matter is a real element of being, for Plato it is not. Of Neoplatonists, Philo (following Plato and the Stoics) also considered matter the principle of imperfection, of limitation and of evil; Plotinus made it empty space, or a pure possibility of Being.

These systems are mentioned here because through them St. Augustine drew his knowledge of Greek philosophy. And in the doctrine of St. Augustine we find the source of an important current of thought that ran through the Middle Ages. He puts forward at different times two views as to the nature of matter. It is first, corporeal substance in a chaotic state; second, an element of complete indetermination, approaching to the me on of Plato. St. Augustine was not directly acquainted with the works of Aristotle, yet he seems to have approached very closely to this thought (probably through the Latin writings of the Neoplatonists) in certain passages of the "Confessions" (cf. Lib. XIII, v, and xxxiii): "For the changeableness of changeable things is capable of all those forms to which the changeable are changed. And what is this? Is it soul? Or body? If it could be said: `Nothing: something that is and is not', that would I say."... "For from nothing they were made by Thee, yet not of Thee: nor of anything not Thine, or which was before, but of concreated matter, because Thou didst create its informity without any interposition of time." St. Augustine does not teach the dependence of quantity upon matter; and he admits a quasi-matter in the angels. Moreover, his doctrine of the rationes semanales (of Stoical origin), which found many adherents among later scholastics, clearly as-signs to matter something more than the character of pure potentiality attributed to it by St. Thomas. It may be noted that Albert the Great, the predecessor of St. Thomas, also taught this doctrine and, further, was of the opinion that the angelic "forms" must be held to have a fundamentum, or ground of differentiation, analogous to matter in corporeal beings.

Following St. Augustine, Alexander of Hales and St. Bonaventure, with the Franciscan School as a whole, teach that matter is one of the intrinsic elements of all creatures. Matter and form together are the principles of individuation for St. Bonaventure. Duns Scotus is more characteristically subtle on the point, which is a capital one in his synthesis. Matter is to be distinguished as: (a) Materia primo prima, the universalized indeterminate element of contingent beings. This has real and numerical unity. (b) Materia secundo prima, united with "form" and quantified. (c) Materia tertio prima, subject of accidental change in existing bodies. For Scotus, who acknowledges his indebtedness to Avicebron for the doctrine (De rerum princip., Q. viii, a. 4), Materia primo prima is homogeneous in all creatures without exception. His system is dualistic. Among later notable scholastics Suarez may be cited as attributing an existence to primordial matter. This is a logical consequence of his doctrine that no real distinction is to be admitted between essence and existence (q.v.). God could, he teaches, "preserve matter without a form as He can a form without matter" (Disput. Metaph., xv, sec. 9). In his opinion, also, quantified matter no longer appears as the principle of individuation. A considerable number of theologians and philosophers have professed his doctrine upon both these points.